But here’s where it gets really interesting. Natural births were also down 5.3 percent on Halloween. Becca Levy, who worked on the study, hypothesizes that a mother’s desire to give or not give birth on a certain date ”might affect a hormonal cascade, which could have an impact on the [birth's] timing.”

The researchers also looked at Valentine’s Day and found the opposite effect: births were up 5.3 percent on the love-themed holiday.